Adapting a Mobile Network

ABSTRACT

In a method for adapting a mobile network, a terminal is connected to a first access node of the mobile network via a first connection and to a second access node via a second connection. The first access node controls a data transmission for the terminal and the second access node assists in the data transmission for the terminal. The method comprises determining whether a quality of at least one of the first connection and the second connection is degraded, acquiring quality degradation information about the degradation of the quality of at least one of the first connection and the second connection based on the step of determining, and adapting the mobile network based on the step of acquiring.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/815,577, filed Mar. 11, 2020, which in turn is a continuation of U.S.patent application Ser. No. 14/761,770, filed Jul. 17, 2015, now issuedas U.S. Pat. No. 10,631,222, which was the National Stage ofInternational Application No. PCT/EP2014/050868, filed Jan. 17, 2014,which claims the benefit of U.S. Provisional Application No. 61/754,322,filed Jan. 18, 2013, each of which is incorporated by reference in itsentirety.

TECHNICAL FIELD

The present invention generally relates to telecommunications, andparticularly relates to methods for adapting a mobile network. Nodes, acommunication system, computer programs, and computer program productsare also described.

BACKGROUND

The present disclosure is described within the context of Long TermEvolution (LTE), i.e. Evolved Universal Mobile Telecommunications System(UMTS) Terrestrial Radio Access Network (E-UTRAN). It should beunderstood that the problems and solutions described herein are equallyapplicable to wireless access networks and user equipments (UEs)implementing other access technologies and standards. LTE is used as anexample technology where the embodiments are suitable, and using LTE inthe description therefore is particularly useful for understanding theproblem and solutions solving the problem.

For ease of understanding, LTE Mobility is described in the following.

Radio Resource Control (RRC) (Third Generation Partnership Project(3GPP) Technical Specification (TS) 36.331, e.g. V10.8.5 (2013-01)) isthe main signaling protocol for configuring, re-configuring and generalconnection handling in the LTE radio access network (E-UTRAN). RRCcontrols many functions such as connection setup, mobility,measurements, radio link failure and connection recovery. Thesefunctions are of relevance for the present disclosure, and are thereforedescribed in some further detail below.

A UE in LTE can be in two RRC states: RRC_CONNECTED and RRC_IDLE. InRRC_CONNECTED state, mobility is network-controlled based on e.g.measurements provided by the UE. I.e. the network decides when and towhich cell an UE should be handed over, based on e.g. measurementsprovided by the UE. The network, i.e. the LTE radio base station (calledevolved Node Base station (eNodeB or eNB), respectively, in E-UTRAN)configures various measurement events, thresholds etc. based on whichthe UE then sends reports to the network, such that the network can makea wise decision to hand over the UE to a stronger cell as the UE movesaway from the present cell.

FIGS. 1A and 1B illustrate a LTE RRC handover procedure according to3GPP TS 36.300, e.g. V11.4.0 (2013-01), FIG. 10.1.2.1.1-1. FIGS. 1A and1B illustrate a LTE RRC handover procedure. In a mobile network 100, aUE 102 is connected to a source eNodeB 104 of a LTE radio accessnetwork, which is controlled by a Mobility Management Entity (MME) 106of a packet switched domain of a core network. A target eNodeB 108 iscontrolled by the MME 106. The user equipment 102 is exchanging datawith a serving gateway 110 of the core network. During a handover, theuser equipment 102 is handed over from the source eNodeB 104 to thetarget eNodeB 108 of the radio access network. Corresponding user datasignaling is indicated by dashed arrows. L3 control signaling isindicated by dotted dashed arrows, and L1/L2 control signaling isindicated by solid arrows. The source eNodeB 104 sends in a first step 1management control information to the user equipment 102, which in turnsends corresponding measurement reports in a step 2 to the source eNodeB104. Thereupon, the source eNodeB 104 performs in a step 3 a handoverdecision, and sends a handover request in a step 4 to the target eNodeB108. After performing admission control in a step 5, the target eNodeB108 sends a handover request acknowledgement in a step 6 to the sourceeNodeB 104, which initiates a RRC connection reconfiguration in a step 7towards the UE 102.

FIG. 2 illustrates a simplified picture of the parts of the LTE Handover(HO) procedure relevant for the disclosure. It should be noted that theHO command is in fact prepared in the Target eNB, but the messagetransmitted via the Source eNB. I.e. the UE sees that the message comesfrom the Source eNB. A mobile network 200 comprises a source eNodeB 204and a target eNodeB 208. A UE 202 is connected to the source eNodeB 204.Subsequent to a step 210, in which a measurement configuration is sentfrom the source eNodeB 204 to the user equipment 202, the user equipment202 performs in a step 212 an A3 event in which a signal strength orsignal quality of the target eNodeB 208 may be detected to be bettercompared to a signal strength or signal quality of the source eNodeB204, respectively, and accordingly reports in a step 214 a measurementreport to the source eNodeB 204. After a corresponding handover decisionin a step 216, the source eNodeB 204 sends a handover request in a step218 to the target eNodeB 208, which in turn sends a handoveracknowledgement in a step 220 to the source eNodeB 204. The sourceeNodeB 204 then sends in a step 222 a handover command to the userequipment 202, which performs in a step 224 a random access procedure inwhich dedicated preambles are submitted to the target eNodeB 208.Further arrows 226-230 relate to a completion of the handover procedure.In the step 226 an uplink (UL) grant and a Tracking Area (TA) may besent from the target eNodeB 208 to the UE 202. In the step 228 a HOconfirm may be sent from the UE 202 to the target eNodeB 208. In thestep 230 a Release context may be sent from the target eNodeB 208 to thesource eNodeB 204. The steps 210, 214, 216, 218, 220, 222, 224correspond to the steps 1, 2, 3, 4, 6, 7, and 11 in FIGS. 1A and 1B.

In RRC_IDLE, mobility is handled by UE-based cell-selection, where anomadic UE 102, 202 selects the “best” cell to camp on, based e.g. onvarious specified criteria and parameters that are broadcasted in thecells. For example, various cells or frequency layers could beprioritized over other, such that the UE 102, 202 tries to camp on aparticular cell as long as the measured quality of a beacon or pilot inthat cell is a threshold better than some other beacon or pilot receivedfrom other cells.

The present disclosure is primarily focusing on problems associated withnetwork-controlled mobility as described above, i.e. for an LTE UE inRRC_CONNECTED state. The problems associated with failing handovers aretherefore described in further detail below.

In a regular situation, and when a RRC_CONNECTED UE 102, 202 is movingout from the coverage of a first cell (also called source cell), itshould be handed over to a neighboring cell (also called target cell orsecond cell) before loosing the connection to the first cell. I.e. it isdesirable that the connection is maintained without no or minimaldisruption throughout the handover, such that the end-user is unaware ofthe ongoing handover. In order to succeed with this, it is necessarythat

-   -   the measurement report that indicates the need for mobility is        transmitted by the UE 102, 202 and received by the Source eNB        104, 204, and    -   the Source eNB 104, 204 has sufficient time to prepare the        handover to the target cell (by, among other things, requesting        a handover from the Target eNB 108, 208 controlling the target        cell), and    -   the UE 102, 202 receives the handover command message from the        network, as prepared by the Target eNB 108, 208 in control of        the target cell and sent via the source cell to the UE 102, 202,        see FIGS. 1A, 1B, and 2.

In addition, and in order for the handover to be successful, the UE 102,202 must finally succeed in establishing a connection to the targetcell, which in LTE requires a successful random access request in thetarget cell, and a subsequent HO complete message. It is noted thatspecifications may differ somewhat in the naming of messages. This doesnot limit the applicability of the present disclosure. For example, thehandover command labeled as HO Command in the step 222 of FIG. 2corresponds to the RRC Configuration Reconfiguration of the step 7 ofFIG. 1A, and the handover confirm message of the step 228 of FIG. 2corresponds to the RRC Configuration Reconfiguration Complete of thestep 11 of FIG. 1A.

Thus, it is clear that in order to succeed all this, it is necessarythat the sequence of events leading to a successful handover is startedsufficiently early, so that the radio link to the first cell (over whichthis signaling takes place) does not deteriorate too much beforecompletion of the signaling. If such deterioration happens before thehandover signaling is completed in the source cell (i.e. first cell),then the handover is likely to fail. Such handover failures (HOFs) areclearly not desirable. The current RRC specification therefore providesvarious triggers, timers, and thresholds in order to adequatelyconfigure measurements, such that the need for handovers can be detectedreliably, and sufficiently early.

In FIG. 2, the exemplified measurement report is triggered by a socalled A3 event in the step 212 which, in short, corresponds to thescenario in which a neighbor cell is found to be an offset better thanthe current serving cell. It should be noted that there are multipleevents that can trigger a report.

It may occur that a UE 102, 202 looses coverage to the cell that the UE102, 202 is currently connected to. This could occur in a situation whena UE 102, 202 enters a fading dip, or that a handover was needed asdescribed above, but the handover failed for one or another reason. Thisis particularly true if the “handover region” is very short. Byconstantly monitoring the radio link quality, e.g. on the physical layeras described in 3GPP TS 36.300, e.g. V11.4.0 (2013-01), TS 36.331, e.g.V11.2.0 (2013-01), and TS 36.133, e.g. V11.2.0 (2013-01), the UE 102,202 itself is able to declare a radio link failure and autonomouslystart a RRC re-establishment procedure. If the re-establishment issuccessful, which depends, among other things, if the selected cell andthe eNB 104, 108, 204, 208 controlling that cell was prepared tomaintain the connection to the UE 102, 202, then the connection betweenthe UE 102, 202 and the eNB 104, 108, 204, 208 can resume. A failure ofa re-establishment means that the UE 102, 202 goes to RRC_IDLE and theconnection is released. To continue a communication, a brand new RRCconnection has then to be requested and established.

In the following, the features dual connectivity and RRC diversity aredescribed.

Dual connectivity is a feature defined from the UE perspective whereinthe UE may simultaneously receive and transmit to at least two differentnetwork points. The at least two network points may be connected to oneanother via a backhaul link such that a UE may be enabled to communicatewith one of the network points via the other network point. Dualconnectivity is one of the features that are being standardized withinthe umbrella work of small cell enhancements within 3GPP Release 12(Rel-12).

Dual connectivity is defined for the case when the aggregated networkpoints operate on the same or separate frequency. Each network pointthat the UE is aggregating may define a stand-alone cell or it may notdefine a stand-alone cell. In this respect, the term “stand-alone cell”may particularly denote that each network point, hence each cell, mayrepresent a separate cell from a perspective of a UE. In contrast,network points not defining a stand-alone cell may be regarded from aperspective of a UE as one same cell. It is further foreseen that fromthe UE perspective the UE may apply some form of Time Division Multiplex(TDM) scheme between the different network points that the UE isaggregating. This implies that the communication on the physical layerto and from the different aggregated network points may not be trulysimultaneous.

Dual connectivity as a feature bears many similarities with carrieraggregation and coordinated multi-point (CoMP). The main differentiatingfactor is that dual connectivity is designed considering a relaxedbackhaul and less stringent requirements on synchronization requirementsbetween the network points. This is in contrast to carrier aggregationand CoMP, wherein tight synchronization and a low-delay backhaul areassumed between connected network points.

Examples of features that dual connectivity will allow in the networkare:

-   -   RRC diversity (e.g. handover (HO) command from source and/or        target); in this respect, the term “RRC diversity” may        particularly denote a scenario in which control signaling can be        transmitted via at least two connections between a network and a        UE;    -   Radio Link Failure (RLF) robustness (failure only when both        links fail);    -   Decoupled uplink (UL)/downlink (DL) (UL to Low Power Node (LPN)        for example with LPD corresponding to a small cell or a pico        cell, DL from macro cell);    -   Aggregation of macro anchor carrier and LPN data booster(s);    -   Selective Handover (e.g., data from/to multiple nodes);    -   Hide UE mobility between smalls cells from Core Network (CN)        with C-plane in macro cell; and    -   Network Sharing (Operators might want to always keep the control        plane and Voice Over IP (VoIP) terminated in their own macro,        but may be willing to offload best effort traffic to a shared        network).

FIG. 3 illustrates the feature of dual connectivity of a UE 302 to ananchor 304 a and a booster 304 b.

A UE 302 in dual connectivity maintains simultaneous connections 334 a,334 b to anchor and booster nodes 304 a, 304 b. As the name implies, theanchor node 304 a terminates the control plane connection towards the UE302 and is thus the controlling node of the UE 302. The UE 302 alsoreads system information from the anchor 304 a. In FIG. 3, the systeminformation and a spatial availability thereof are indicated by a dashedcircle. In addition to the anchor 304 a, the UE 302 may be connected toone or several booster nodes 304 b for added user plane support. In thisrespect, the term “booster” may denote that a performance of a UE interms of its data peak rate may be improved, since user plane data maybe additionally transmitted via the booster. To this end, a transmissionfrequency employed by the anchor may be different from a transmissionfrequency employed by the booster.

The anchor and booster roles are defined from a UE 302 point of view.This means that a node that acts as an anchor 304 a to one UE 302 mayact as booster 304 b to another UE 302. Similarly, though the UE 302reads the system information from the anchor node 304 a, a node actingas a booster 304 b to one UE 302, may or may not distribute systeminformation to another UE 302.

FIG. 4 illustrates a control and user plane termination in an anchornode and a booster node. This protocol architecture may represent anexemplary protocol termination compliant with dual connectivity and RRCdiversity. The protocol architecture shown in FIG. 4 is proposed as away forward for realizing dual connectivity in LTE Rel-12 in deploymentswith relaxed backhaul requirements. In the user plane 436 a distributedPacket Data Convergence Protocol (PDCP)/Radio Link Control (RLC)approach is taken where the booster and anchor terminate the user planes436 of their respective bearers, with a possibility to realize userplane aggregation via Multipath Transmission Control Protocol (MPTCP)which may offer a split of traffic to several connections. In thecontrol plane 434, the RRC and Packet Data Convergence Protocol (PDCP)are centralized at the anchor, with a possibility to route RRC messagesvia the anchor, the booster, or even simultaneously at both links. Forease of completeness, “NAS” may represent a Non Access Stratum protocollayer, “RLC” may represent a Radio Resource Control protocol layer,“MAC” may represent Medium Access Control protocol layer, and “PHYS” mayrepresent a Physical layer.

In a further exemplary protocol termination enabling dual connectivityand RRC diversity, RRC is terminated in the anchor node, and PDCP isavailable both for the anchor node and the booster node.

However, problems described in the following might occur.

A problem may relate to handover failures and radio link failures forscenarios in which a UE is connected to one network point, hence onecell. In the following, handover and radio link failure robustness isdescribed.

The recent and rapid uptake of Mobile Broadband has led to a need forincreasing the capacity of cellular networks. One solution to achievesuch a capacity increase is to use denser networks consisting of several“layers” of cells with different “sizes”: Macro cells ensure largecoverage with cells encompassing large areas, while micro-, pico- andeven femto-cells are deployed in hot-spot areas where there is a largedemand for capacity. Those cells typically provide connectivity in amuch smaller area, but by adding additional cells (and radiobase-stations controlling those cells), capacity is increased as the newcells off-load the macro cells.

FIG. 5 illustrates a UE 502 moving out from a pico cell area of a picocell 538 into macro cell area of a macro cell 540. A movement directionof the user equipment 502 is indicated by an arrow 542. This figure mayillustrate a typical scenario for a handover of a UE 502.

The different “layers” of cells can be deployed on the same carrier(i.e. in a reuse-1 fashion in which all neighboring cells may use thesame frequency), the small-cells could be deployed on a differentcarrier, and the different cells on the various layers could even bedeployed using different technologies (e.g. 3G/High Speed Packet Access(HSPA) on the macro- and micro-layer, and LTE on the pico-layer as onenon-exclusive example). In this respect, the term “layer” mayparticularly denote a higher abstraction level of a cell with respect toa transmission frequency or carrier employed in the cell.

There is currently a large interest for investigating the potential ofsuch Heterogeneous Networks, and operators are interested in suchdeployments. However, it has also been found that such HeterogeneousNetworks may result in an increased rate of handover failures, asbriefly discussed above. One reason is that the handover region inHeterogeneous Networks may be very short, meaning that the handovermight fail since the UE lost coverage to the source cell before thehandover to a target cell could be completed. For example, when a UEleaves a pico-cell, it may happen that the coverage border of the picois so sharp, that the UE fails to receive any handover command towards amacro before loosing coverage to the pico, see FIG. 5 or 6.

FIG. 6 illustrates a handover region of a pico/macro cell change versusa macro/macro cell change. A network comprises a pico cell 638, a marcocell 640 a, and a further macro cell 640 b. An abscissa 644 of thediagram may represent a Reference Signal Received Power (RSRP), and anordinate 646 of the diagram may represent a distance. A curve 666 mayrepresent the RSRP perceived by a UE from the macro cell 640 a, a curve668 may correspond to the RSRP perceived by a UE from the pico cell 638,and a curve 670 may represent the RSRP perceived by the UE from theanother macro cell 640 b. A handover region 672 from the macro cell 640a to the pico cell 638 and vice versa is small compared to a handoverregion 674 between the macro cells 640 a, 640 b.

Similar problems could occur when a UE connected to a macro cellsuddenly enters a pico cell on the same carrier: It could now happenthat the control channels of the pico cell interferes with the signalsthat the UE needs to receive from the macro cell in order to completethe handover, and the handover thus fails.

In order to investigate the consequences of increased handover failuresand solutions to mitigate those, 3GPP is currently working onevaluations and technical solutions for amendments, as described in TR36.839, e.g. V11.1.0 (2013-01).

In the following, key performance indication (KPI) degradation and aneed for drive testing is described. In this respect, the term “keyperformance indication” may particularly denote information collected bya network, which information may relate to a performance characteristicof the network such that a corresponding managing network operator mayaccordingly adapt the network. For example, a KPI may relate to handoverfailures and may indicate information such as how often a handover mayoccur, in which area the handover may occur, a reason for the occurrenceof the handover etc. The term “drive testing” may particularly denote aprocedure in which dedicated testing device, e.g. a user equipment, maymove through the network, e.g. may drive around, and may test networkcharacteristics related to e.g. connectivity. In one option, an entity,e.g. a software may be installed spatially fixed in the network and maycollect corresponding information from user equipments in the network.

Today it is very difficult to determine if a KPI problem experienced ata certain location in a radio network is due to that a Cell does notreceive UE transmission or if it is the UE that does not receive thecell transmission or both. The current typical way of trouble shootingis to make drive testing and collect both Cell traces with time stampedevents/transmissions and UE trace with events/transmissions is collectedfrom the UE's used for drive testing. Here, the term “trace” may referto a collection of logged information.

In 3GPP efforts have been made to support that UE collect someinformation when experiencing problems with the connection or problemsin getting access to the system and then when connectivity isestablished to the network (NW) at a later time when a connection isestablished the NW can ask the UE to transmit the collected information.The collected information has time stamp information based on an UEinternal clock and also location information.

Drive testing and using specific UE's for drive testing may not alwaysbe able to discover intermittent faults or drive into locations wherethe problem actually occurs. If it is a UE vendor specific problem theUE used for drive testing may not have the same kind of fault as some ofthe UE's used by subscribers in the network. On top of that regulardrive testing is typically very expensive. There is a large cost forcollecting the data and also a cost when data is analyzed. The dataanalysis can be costly and difficult due to that drive testers need tocollect all data on rather detailed level and hope that the intermittentfault appears and are captured in the data collected during drivetesting amongst the large amount of data collected.

Assuming a system where a UE can be simultaneously connected to severalcells, it is currently unclear how the UE shall evaluate radio linkfailures and how the system shall react upon these radio link failuresor other connectivity issues of some of the maintained connections.

Moreover, KPI evaluation by the radio network for UEs experiencing radiolink problems in certain locations at a certain time is problematic dueto the degraded connectivity to the UE in these situations. With thecurrent system, the evaluation cannot be done immediately after thefault and is usually based on reports or (costly) drive tests. Animmediate adaption of the system possibly improving the KPIs is thus notpossible.

SUMMARY

It is an object of the present invention to provide measures with whicha network adaption of a mobile network in a case a degradation of aquality of a connection of at two connections between an access node ofthe mobile network and the terminal may be enabled in an improved way.It is a further object of the present invention to provide correspondingmethods, a terminal, nodes, a mobile network, computer programs, andcomputer program products.

The objects above are solved by methods, a terminal, nodes, a mobilenetwork, computer programs and computer program products according tothe independent claims.

According to a first exemplary aspect, a method for adapting a mobilenetwork is provided. A terminal is connected to a first access node ofthe mobile network via a first connection and to a second access nodevia a second connection. The first access node controls a datatransmission for the terminal and the second access node assists in thedata transmission for the terminal. The method comprises determiningwhether a quality of at least one of the first connection and the secondconnection is degraded, acquiring quality degradation information aboutthe degradation of the quality of at least one of the first connectionand the second connection based on the step of determining, and adaptingthe mobile network based on the step of acquiring.

According to a second exemplary aspect, a method for adapting a mobilenetwork is provided. A terminal is connected to a first access node ofthe mobile network via a first connection and to a second access nodevia a second connection. The first access node controls a datatransmission for the terminal and the second access node assists in thedata transmission for the terminal. The method is performed by theterminal and comprises determining whether a quality of at least one ofthe first connection and the second connection is degraded, andacquiring quality degradation information about the degradation of thequality of at least one of the first connection and the secondconnection based on the step of determining particularly for adaptingthe mobile network.

According to a third exemplary aspect, a method for adapting a mobilenetwork is provided. A terminal is connected to a first access node ofthe mobile network via a first connection and to a second access nodevia a second connection. The first access node controls a datatransmission for the terminal and the second access node assists in thedata transmission for the terminal. The method is performed by the firstaccess node and comprises acquiring quality degradation informationabout a degradation of a quality of at least one of the first connectionand the second connection, and adapting the mobile network based on thestep of acquiring.

According to a fourth exemplary aspect, a method for adapting a mobilenetwork is provided. A terminal is connected to a first access node ofthe mobile network via a first connection and to a second access nodevia a second connection. The first access node controls a datatransmission for the terminal and the second access node assists in thedata transmission for the terminal. The method is performed by thesecond access node and comprises adapting the mobile network based on aquality of at least one of the first connection and the secondconnection being degraded.

According to a fifth exemplary aspect, a terminal for adapting a mobilenetwork is provided. The terminal is connected to a first access node ofthe mobile network via a first connection and to a second access nodevia a second connection. The first access node controls a datatransmission for the terminal and the second access node assists in thedata transmission for the terminal. The terminal comprises adetermination unit adapted to determine whether a quality of at leastone of the first connection and the second connection is degraded, andan acquiring unit adapted to acquire quality degradation informationabout the degradation of the quality of at least one of the firstconnection and the second connection based on the determinationparticularly for adapting the mobile network.

According to a sixth exemplary aspect, an access node for adapting amobile network is provided. A terminal is connected to the access nodeof the mobile network via a connection and to another access node viaanother second connection. The access node controls a data transmissionfor the terminal and the another access node assists in the datatransmission for the terminal. The access node comprises an acquiringunit adapted to acquire quality degradation information about adegradation of a quality of at least one of the first connection and thesecond connection, and an adapting unit adapted to adapt the mobilenetwork based on the acquired quality degradation information.

According to a seventh exemplary aspect, an access node for adapting amobile network is provided. A terminal is connected to the access nodeof the mobile network via a connection and to another access node viaanother connection. The another access node controls a data transmissionfor the terminal and the access node assists in the data transmissionfor the terminal. The access node comprises an adapting unit adapted toadapt the mobile network based on, particularly subsequent to, a qualityof at least one of the connection and the another connection beingdegraded.

According to an eighth exemplary aspect, a mobile network is provided.The mobile network comprises a terminal according to the fifth exemplaryaspect, a first access node according to the sixth exemplary aspect anda second access node according to seventh exemplary aspect.

According to a ninth exemplary aspect, a computer program is provided.The computer program, when being executed by a processor, is adapted tocarry out or control a method for adapting a mobile network according toany one of the first, second, third or fourth exemplary aspect.

According to a tenth exemplary aspect, a computer program product isprovided. The computer program product comprises program code to beexecuted by at least one processor, thereby causing the at least oneprocessor to execute a method according to any one of the first, second,third or fourth exemplary aspect.

The foregoing and other objects, features and advantages will becomemore apparent in the following detailed description of the presentdisclosure as illustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are flow diagrams illustrating a signaling exchange fora handover procedure.

FIG. 2 is a flow diagram illustrating a signaling exchange for ahandover procedure.

FIG. 3 is a block diagram illustrating a mobile network used inconnection with dual connectivity of a terminal.

FIG. 4 is a diagram illustrating a control plane and user planeterminating in access nodes.

FIG. 5 is a block diagram illustrating a LTE mobile network.

FIG. 6 is a diagram illustrating a signal strength of a LTE mobilenetwork depending on a distance.

FIG. 7 is a flow chart illustrating a method for adapting a mobilenetwork according to an embodiment.

FIG. 8 is a flow diagram illustrating a method for adapting a mobilenetwork according to another embodiment.

FIG. 9 is a flow diagram illustrating a method for adapting a mobilenetwork according to another embodiment.

FIG. 10 is a block diagram illustrating a terminal for adapting a mobilenetwork according to an embodiment.

FIG. 11 is a block diagram illustrating an access node for adapting amobile network according to an embodiment.

FIG. 12 is a block diagram illustrating an access node for adapting amobile network according to another embodiment.

DETAILED DESCRIPTION

According to the exemplary aspects, in a data transmission for aterminal, data may be transmitted from a first access node to theterminal via a first connection and data duplicates may be sent from asecond access node to the terminal via a second connection. Here, theterm “data transmission” may relate to transmitting signaling dataand/or payload data in an uplink direction from the terminal to themobile network and/or in a downlink direction from the mobile network tothe terminal. In order to enable the terminal to receive duplicate datafrom the first access node and the second access node, the first accessnode may have duplicated the respective data and may have sent the dataduplicates to the second access node via a backhaul connection betweenthe first access node and second access node. The first connection andthe second connection may be independent from one another, and maycomprise respective radio bearers to be established related to the datatransmission.

In such a communication scenario, the first access node may control thedata transmission for the terminal and the second access node may assistin the data transmission for the terminal. In this respect, the term“the first access node controlling a data transmission of the terminal”may particularly denote to a control, by the first access node, ofresource allocation for uplink and/or downlink data transmission for theterminal and/or a connectivity state of the terminal. Hence, the firstaccess node can be also referred to as an anchor node for the datatransmission of the terminal, for example, always being employed for thedata transmission for the terminal. Such a communication scenario may beaccomplished in LTE by terminating a protocol related to the allocationof resources via the air interface between the terminal and the firstaccess node, particularly a RRC protocol, in the first access node.Alternatively, a PDCP protocol may be terminated in the first accessnode. In particular, the term “the second access node assisting in thedata transmission for the terminal” may particularly denote that thesecond access node may be free of a capability of controlling the datatransmission to the terminal, but may relay the uplink and/or downlinkdata transmission between the access node and the terminal. Inparticular, the second access node can be referred to as a booster nodefor the data transmission of the terminal, for example, being employedfor the data transmission for the terminal as relay node. Hence, asexplained above, information sent between the first access node and theterminal may be duplicatedly sent between the first access node and theterminal via the second access node.

In this communication scenario, at least one of the first and secondconnections may comprise a degraded quality. In order to accomplish asuitable mobile network adaption in case of such a quality degradation,a quality of the first connection and/or the second connection may bedetermined, respective quality degradation information indicating that aquality of the first connection and/or the second connection may bedegraded may be acquired based on the step of determining, and, based onthe step of acquiring, the mobile network may be adapted. In thisrespect, the term “acquiring information” may relate to an entityobtaining information by means of internally determining informationand/or obtaining information by means of receiving information over themobile network.

Accordingly, connectivity degradation of a connectivity between theterminal and the first access node and/or the second access node may behandled in an efficient, easy and fast way. An overall systemperformance may be therefore improved.

With reference to embodiments explained in this disclosure, the firstaccess node may be referred in described embodiments as “Source eNB” andthe first connection may refer to an “anchor” connection 332 a in FIG.3. The second access node may be referenced in the described embodimentsas “Assisting eNB”, and the second connection may refer to the “booster”connection 332 b in FIG. 3. It is noted that the target eNB 108, 208described in connection with FIGS. 1A, 1B, and 2 may also represent anaccess node adapted to control the data transmission for the terminaldepending on being a transmission controlling access node or not.

Next, embodiments related to the method according to first exemplaryaspect will be described. These embodiments also apply to the methodsaccording to second, third and fourth exemplary aspects, the terminalaccording to the fifth exemplary aspect, the first access node accordingto sixth exemplary aspect, the second access node according to theseventh exemplary aspect, the mobile network according to the eighthexemplary aspect, the computer program according to the ninth exemplaryaspect and the computer program product according to the tenth exemplaryaspect.

The step of adapting the mobile network may comprise adapting at leastone connection between the terminal and the mobile network based on thestep of determining. In particular, the terminal may be part of themobile network.

With respect to the step of adapting, in one variant of the method, thestep of determining may result in the first connection comprising adegraded quality, and the step of adapting may comprise maintaining theconnection not comprising the degraded quality. In this case, theconnection not comprising the degraded quality may be the secondconnection.

Alternatively or additionally, the step of determining may result in thefirst connection comprising a degraded quality, and the step of adaptingmay comprise handing, by the first access node, the terminal over fromthe first access node to the second access node and disconnecting thefirst connection. For example, the first access node may initiate thehandover of the terminal by sending a handover request to the secondaccess node. The second access node may then forward or relay thehandover request to the terminal. The first access node may stopcontrolling the data transmission of the terminal. In LTE the latterperformed step may relate to stop RRC diversity. In this respect, RRCdiversity employed in the first access node may relate to a sending ofdata directly to the terminal and to a sending of duplicates of thedata, which may be sent by the first access node to the terminal, to thesecond access node for relaying them by the second access node to theterminal. The data may comprise control signaling. Accordingly, stoppingRRC diversity may refer to not duplicating the sent data anymore, thusmaintaining only the direct connection to the terminal to keep legacyfunctionality. This legacy connection may be handed over to the secondaccess node. Or in other words, particularly with respect to LTE, thelatter may relate to stopping RRC signal duplication and forwarding tothe second access node. In the above case the first access node maycontrol the disconnection of the terminal, for example by sending a RRCreconfiguration request message to the terminal via the second accessnode. In the above case, the step of adapting may further comprisetransferring, by the first access node, control capabilities forcontrolling the data transmission of the terminal from the first accessnode to the second access node. For example, a signaling bearer betweenthe first access node and the terminal may be transferred to the secondaccess node, which bearer may transport a control signaling. Inparticular, the latter mentioned embodiments may be described later withreference to steps 8, 9, 11 and a resulting step or state 999 of FIG. 9.

In another further variant of the method, the step of determining mayresult in the second connection comprising a degraded quality, and thestep of adapting comprise requesting, by the first access node, todisconnect the second connection, and stopping to employ the secondaccess node for the data transmission for the terminal. In particular,the step of stopping to employ the second access node for the datatransmission may comprise stopping to duplicate the data sent from thefirst access node to the terminal and stopping to send the duplicateddata to the second access node. In particular, this step may be embodiedas stopping RRC diversity, relating to not duplicating the data ormessages anymore which may be to be sent to the second access node. Amessage related to the disconnect request may be embodied as a Stop RRCrelaying message explained with reference to FIG. 8. Thus only a directconnection from the first access node to the UE may be maintained, thelatter referring to as legacy functionality of the first access node ofthe mobile network. This embodiment may be described later withreference to FIG. 8.

With regard to the step of acquiring, in a first variant of the method,the step of determining may result in one connection of the firstconnection and the second connection comprising a degraded quality, andthe step of acquiring may comprise sending, by the terminal, the qualitydegradation information to the access node of the first access node andthe second access node whose connection to the terminal might notcomprise the degraded quality. In this case the quality degradationinformation may be sent via the connection not comprising the degradedquality. For example, the quality degradation information may be sent tothe first access node, if the second connection may have failed, as willbe explained with reference to FIG. 8. The quality degradationinformation may be sent to the second access node, if the firstconnection may have failed, and may be relayed or forwarded by thesecond access node to the first access node, as may be explained withreference to FIG. 9.

In another variant, the step of determining may result in one connectionof the first connection and the second connection comprising a degradedquality, and the step of acquiring may comprise sending, by theterminal, the quality degradation information to the access node of thefirst access node and the second access node whose connection to theterminal may comprise the degraded quality. In this case the qualitydegradation information may be sent via the connection comprising thedegraded quality and/or may be sent via a further connection between theterminal and the access node. This further connection may be differentfrom the first and second connection. This measure may beneficiallyenable that the terminal may inform the access node whose connectionwith the terminal has been identified to be degraded in a transmissiondirection from the access node to the terminal without a necessity ofinvolving the other access node. The access node may then initiate anadaption of the mobile network without unnecessary delay. It may beassumed for this measure that the connection in a transmission directionfrom the terminal to the access node may comprise a sufficient highquality for successfully transmitting the quality degradationinformation.

The connection comprising the degraded quality may have failed. In thiscase the quality degradation information may comprise or may be embodiedas a failure notification indication, particularly a RLF warningindication. The failure notification indication may represent anindividual indication, particularly included in a conventional messageor in a new type message, or may be a specific type of message.

The quality degradation information may comprise or may be embodied asat least one information of the following kind of information.Information according to a first option may comprise or may be embodiedas cell identification indication indicative of an identification of anarea, particularly a cell, being served by the access node associatedwith the failed connection, particularly an PCell Identification (ID), acell global ID, a physical cell ID, or a carrier frequency of the cell.Information according to a second option may comprise or may be embodiedas information about measurement results obtained for the area served bythe access node associated with the failed connection and obtained for aprevious time period. Information according to a third option maycomprise or may be embodied as information about a measurement resultobtained for an area, particularly a cell, served by the access nodeassociated with the not failed connection and obtained for a previoustime period. Information according to fourth option may comprise or maybe embodied as information about a measurement result obtained for atleast one further area, particularly a further cell, served by a furtheraccess node distinct from the first access node and second access nodeand obtained for a previous time period, particularly an identifier forthe measurement. Information according to a fifth option may comprise ormay be embodied as a connection indication indicative of the failedconnection. Information according to a sixth option may comprise or maybe embodied as a timer of the failure of the failed connection.Information according to a seventh option may comprise or may beembodied as a failure reason.

In such a case the failure reason may comprise at least one of thefollowing kind of failure reasons. In a first option, the failure reasonmay comprise an expiration of a timer with the timer being started aftera predetermined number of counter fulfillments of a condition and thetimer being stopped after a predetermined number of counter fulfillmentsof another condition. For example the latter may correspond to an “outof sync” failure in LTE which may refer to a RLF timer expiry. Anotherfailure reason may comprise a maximum of scheduling requests having beensent over the respective connection particularly without receiving aresponse. For example the latter may correspond in LTE to a maximumnumber of scheduling requests having been reached. A further failurereason may comprise a maximum of retransmission of data having been sentby the terminal over the respective connection. For example the lattermay correspond in LTE to a maximum number of RLC retransmissions havingbeen reached. In case of RLC retransmissions, the UE may retransmitdata, if no reply may be received until a maximum number ofretransmissions may be reached. A further failure reason may comprise amaximum of unsuccessful random access attempts having been sent by theterminal over the respective connection without receiving a datatransmission over the respective connection. For example the latter maycorrespond in LTE to a Random Access Channel (RACH) failure.

The at least one information mentioned above may be sent together withthe failure notification indication in one message or may be sentsubsequent to the sent failure notification indication for the step ofacquiring.

Respecting the step of determining, in a first variant of the method,the step of determining may be performed by the terminal and maycomprise evaluating the quality of the first connection and evaluatingthe quality of the second connection. In this case the step ofevaluating of the quality of the first connection and the step ofevaluating the quality of the second connection may be performedindependently of one another. Additionally or alternatively, therespective step of evaluating comprises evaluating a synchronization ofthe terminal with the respective access node with respect to the datatransmission over the respective connection. In particular, adegradation of the quality of the respective connection may bedetermined, if the terminal may be not suitably synchronized for thedata transmission over the respective connection. In particular, thedetermined degradation of the quality of the connection may correspondto a connection failure.

In a further variant of the method, the step of determining maycomprise, particularly for each of the first and second connections,using a timer in the terminal and a counter in the terminal. The countermay be associated with a fulfillment of a condition, and a degradationof the quality of the respective connection may be determined, if thetimer may expire with the timer being started after a predeterminednumber of the counter fulfillments of the condition, and the timer beingstopped after a predetermined number of counter fulfillments of anothercondition. In particular, the timer may correspond to the T310 timer andthe counter may correspond to the constant N310. In particular, the sameor different type of timers and/or counters can be employed for thefirst and second connections.

In a further variant, the step of determining comprises, particularlyfor each of the first and second connections, using a timer in theterminal and counters in the terminal, each of the counters beingassociated with a fulfillment of a condition, wherein a degradation ofthe quality of the respective connection may be determined, if the timermay expire, the timer being started after a predetermined number of thecounter fulfillments of the condition, and the timer being stopped aftera predetermined number of another counter fulfillments of anothercondition. In particular, the timer may correspond to the T310 timer andthe counters may correspond to the counters or constants N310, N311. Inparticular, the same or different type of timers and/or counters can beemployed for the first and second connections.

With respect to the above described embodiments, the timer T310 and thecounter N310, 311 may represent a legacy timer and a legacy counter,respectively. The counter N310 may count condition fulfilments, in orderto start the timer T310. Such condition fulfillment may relate to acondition whether a Signal to Interference and Noise Ratio (SINR)perceived by the terminal may be below a threshold. The counter N311 maycount condition fulfilments, in order to stop the timer T310. Suchcondition fulfillment may relate to a condition whether the SINRperceived by the terminal may be above a further threshold. Hence, thetimer T310 may be started after the counter N310 may have counted apredetermined number of condition fulfillments of the conditionassociated with the counter N310, and the timer T310 may stop after apredetermined number of condition fulfillments of the conditionassociated with the counter N311 have been counted. A degraded qualityis detected, if the timer T310 may expire and the predetermined numberof condition fulfillments of the condition associated with the counterN311 might have not been counted.

The respective step of evaluating described above may compriseevaluating whether a maximum of scheduling requests may have been sentover the respective connection. Additionally or alternatively, therespective step of evaluating may comprise evaluating whether a maximumof retransmission of data may have been sent by the terminal over therespective connection. Additionally or alternatively, the respectivestep of evaluating may comprise evaluating whether a maximum ofunsuccessful random access attempts may have been sent by the terminalover the respective connection without receiving a data transmissionover the respective connection.

The connection comprising the degraded quality might have not failed.

In such a case the step of determining may result in the firstconnection comprising the degraded quality and the second connection notcomprising a degraded quality, and the step of adapting may compriseswitching a functionality of the first access node and the second accessnode with respect to controlling the data transmission for the terminal.Hence, the first access node may turn into a transmission assistingaccess node and the second access node may turn into a transmissioncontrolling access node.

In this case the quality degradation information may comprise or may beembodied as a channel quality indication, particularly a Chanel QualityIndication report.

The step of acquiring may comprise sending by one access node of thefirst access node and the second access node to the other access of thefirst access node and the second access node the quality degradationinformation. For example, the step of determining may be performed bythe second access node which may monitor a parameter associated with thechannel quality information and/or may determine a value of theparameter.

With regard to the step of adapting, in another variant of the method,the step of determining may also result in the first connection and thesecond connection may have failed, and the step of adapting may compriseestablishing a further connection between the terminal and a furtheraccess node of the mobile network. In accordance with this embodiment,the step of acquiring may be performed by the terminal, and/or the stepof establishing may be initiated by the terminal. The further accessnode may be distinct from the first access node and the second accessnode or may be one of the first and second access nodes. Hence, thefirst connection and/or the second connection may be re-established.

Particularly in the later mentioned case in which the step ofdetermining may result in the first connection and the second connectionhaving failed, the step of acquiring may comprise sending, by theterminal, one or more connection failure reports, particularly radiolink failure reports, to the further access node of the mobile network.The one or more connection failure reports may comprise informationabout the first and/or second connection or about all connections of theterminal. The information may relate to the connection failure of theparticular connection or connections. For example, one connectionfailure report may be sent from the terminal in which the informationabout the first and/or second connection may be included. Alternatively,at least two connection failure reports may be sent by the terminal, inwhich information about the connection failure of specific connectionsmay be included. The connection failure report may be sent after theterminal having successfully established a connection to the furtheraccess node.

With respect to the step of acquiring, in another variant of the method,the method may further comprise determining at least one key performanceindication for the mobile network, and the step of adapting may compriseadapting at least one system setting of the mobile network based on theat least one key performance indication. The step of adapting of thesystem settings may be alternatively or additionally based on qualitydegradation information obtained, particularly sent in a RLF indicationor RLF reports. An objective of this adaption may be the improvement ofone of the key performance indicators in the network. In this respect,the system setting may relate to a characteristic of the first and/orsecond access node or may relate to a characteristic of a further accessnode of the mobile network. The above described embodiments for adaptingthe mobile network may describe an immediate or ad hoc adaption of themobile network, and this embodiment related to the adaption of thesystem setting may describe an overall adaption of the mobile network onan intermediate or long term time scale.

Particularly in relation to the later mentioned network adaption, thestep of determining may be performed by the terminal and the step ofacquiring may be performed by the terminal and an access node of thefirst access node and the second access node. The method may comprise,acquiring, by the access node, further quality degradation informationindicating a quality of the connection between the terminal and theaccess node being degraded. The step of adapting may be performed basedon the acquired quality degradation information and the determinedfurther quality degradation information. The further quality degradationinformation may relate to whether a maximum number of resynchronizationattempts performed by the access node may have been reached, whether amaximum number of scheduling requests sent by the access node may havebeen reached and/or whether a maximum of number of RLC retransmissionsmay have been reached by the access node. In order to correctly combinethe quality degradation information and the further quality degradationinformation, each of the latter two information may be associated with acorresponding time stamp.

In such an embodiment, the terminal may determines and send a RLFwarning or a CQI report to the access node. The access node may alsodetermine internal connection quality and then may decide which networkadaption to perform with respect to quality of a downlink and/or uplinkdirection of the connection being degraded. This adaption may relate toa long term adaption described above.

With respect to the method according to the second exemplary aspect,quality degradation information embodied as a RLF indication may beembodied as or transmitted in a RRC message. Since RRC may be terminatedin the first access node, i.e. RRC messages from the terminal to thesecond access node may always terminate in the first access node.Quality degradation information embodied as a CQI report and being sentto the second access node may not be automatically forwarded to thefirst access node, but as explained above the second access node may beenabled to perform such a step. The first access node may be thereforeenabled to perform the step of adapting based on the acquired qualitydegradation information.

With respect to the method according to the third exemplary aspect, thesecond access node may, in one option described later with reference toFIG. 8, adapt the mobile network by stopping RRC relaying. In a furtheroption described later with reference to FIG. 9, the second access nodemay acquire a RLF indication, and may adapt the mobile network byupgrading to the first access node, and may optionally forward the RLFindication to the first access node. In a third option described laterin connection with the CQI report, the second access node may receive aCQI report and may adapt the mobile network, and may optionally forwardthe CQI report to first access node.

In the following with reference to FIGS. 7 to 12, further embodimentswill be described in more detail within the context of LTE. It is notedthat the terms “terminal” and “user equipment” may be used in aninterchangeable way throughout this application. One or more embodimentsare based on the assumption that the UE can communicate independentlyvia two maintained connections. To provide radio link failure (RLF)diversity as well, the UE shall trigger the standardized RLF procedureonly if both links are out-of-sync. In this respect, the term “out-ofsync” may particularly denote that an user equipment may have lostsynchronization to an access node in that the user equipment may not beable to decode synchronization information in terms of e.g. referencesignals properly. If only one of the maintained connections fails,however, a different UE behavior must be enforced. With the embodimentsthe UE is able to inform the involved eNBs with the help of a new RRCRLF warning message about the RLF of one of the links, and the eNBs areable to quickly react upon this information by stopping the RRCdiversity connection and/or handing over the UE completely to one of theinvolved eNBs. The eNB may also decide to move potential bearers mappedover the failed link to another link.

FIG. 7 illustrates steps of a method according to an embodiment. Arelated communication scenario comprises an user equipment UE, a firstaccess node called a serving base station, and a second access nodecalled an assisting base station. According to a first step 776, theuser equipment is connected to the serving base station. This basestation may request control signaling relaying assistance from anassisting base station for the UE. In a further step 778, the UE isconfigured to transmit and receive control signaling both via theserving base station and the assisting base station with the assistingbase station relaying the control signaling from and to the serving basestation, respectively. Further, the UE may monitor the radio links ofall maintained connections separately. In a further step 780, if the UEregisters or detects a radio link failure for one of the links, the UEmay stop transmission on that link and may transmit a radio link failurewarning indication via a second maintained link, possibly relayed by theassisting base station, to the serving base station. In a step 782performed according to a first option of the method, if the failed linkmay be towards the assisting base station, the serving base station mayissue the UE to reconfigure to be solely connected to the serving basestation, and may issue the assisting base station to stop assistance.Alternatively, in a step 784 performed according to a second option ofthe method, if the failed link is towards the serving base station, theserving base station may stop transmission and may handover the UE tothe assisting base station which may become the serving base station forthe UE itself.

Moreover, with the information obtained from the RLF-warning of one linkand the information of another maintained connection E-UTRAN is quicklyable to combine these information, learn about UE RLF failure reasons,their statistics and can apply necessary adaptations.

Embodiments are based on the assumption that the UE can communicateindependently via two maintained connections. To provide radio linkfailure (RLF) diversity as well, the UE shall trigger the standardizedRLF procedure only if both links are out-of-sync. If only one of themaintained connections fails, however, a different UE behavior must beenforced as explained in the following.

In the following, procedures according to embodiments are described inmore detail.

In FIG. 8 and FIG. 9 the signaling involved in the setup of the RRCconnection as well as the reaction upon RLF of one of the links isdescribed. In FIG. 8, a mobile network 800 comprises an user equipment802, a source eNodeB 804, and an assisting eNodeB 808. In FIG. 9, amobile network 900 comprises an user equipment 902, a source eNodeB 904,and an assisting eNodeB 908. Steps in FIGS. 8, 9 are labelled by integernumbers. RRC anchor functionality of the source and target eNodeBs 804,904, 908 is indicated by a bold solid line and is referenced by areference numeral 886, 986. RRC relay capability of the assisting eNodeB808, 908 is indicated in FIGS. 8, 9 by a bold dashed line and isreferenced by a reference numeral 888, 988.

According to FIGS. 8, 9, in a step 1, a measurement configuration issent from the source eNodeB 804, 904 to the user equipment 802, 902. Ina step 2, an early measurement report is sent from the UE 802, 902 tothe source eNodeB 804, 904. The early measurement report may be issuedin response to a A3 event explained with reference to FIG. 2. In asubsequent step 3, an RRC assistance request is sent from the sourceeNodeB 804, 904 to the assisting eNodeB 808, 908. In a next step 4, anRRC assistance response including RRC reconfiguration information issent from the assisting eNodeB 808, 908 to the source eNodeB 804, 904.In a next step 5, the RRC-reconfiguration information is sent from theassisting eNodeB 808, 908 to the source eNodeB 804, 904. ARRC-reconfiguration is sent from the source eNodeB 804, 904 to the UE802, 902 in a step 5. In a step 890, 990, the source eNodeB 804, 904starts RRC diversity. In a step 892, 982, the assisting eNodeB 808, 908starts RRC relaying. In a next step 6, the UE 802, 902 sends asynchronization and RACH procedure request towards the assisting eNodeB808, which accordingly sends a response to the UE 802, 902.

Hence, the UE 802, 902 is first configured with a measurementconfiguration (1) issuing an early measurement report (2). Thismeasurement may relate to a source cell, assisting cell or differentcells. Upon reception of this measurement report in the source eNB 804,904 it will (if required) request an RRC diversity peering (3) with theassisting eNB 808, 908, which acknowledges this request (4) and includesthe RRC-reconfiguration for the UE 802, 902 to setup RRC diversitytransmission and reception, which the source eNB 804, 904 will forwardto the UE 802, 902 (5). At this point the source eNB 804, 904 will gointo RRC diversity state where RRC messages are transmitted and receivedto the UE 802, 902 directly and additionally send to/received from theassisting eNB 808, 908 for relaying to/from the UE 802, 902. The UE 802,902 will start a RACH procedure towards the assisting eNB 808, 908 tobecome synchronized to it (6).

In FIG. 8 the reaction procedure for RLF to the assisting cell isdescribed, while in FIG. 9 the procedure for RLF to the source cell isdescribed.

In the following, a reaction to the assisting eNB 808 out-of-sync isdescribed. As illustrated in FIG. 8, a RLF between the UE 802 and theassisting eNodeB 808 occurs in a step 884. In a step 896, the UE 802stops transmitting to the assisting eNodeB 808. In a step 7, the UE 802sends a RLF warning to the source eNodeB 804, which in turn stops in astep 8 RRC relaying to the assisting eNodeB 808. In steps 898, 899, thesource eNodeB 804 stops RRC diversity and the assisting eNodeB 808 stopsRRC relaying, respectively. In steps 10 and 11, the source eNodeB 804sends a RRC reconfiguration request to the UE 802 and the UE 802 sends aRRC reconfiguration command to the source eNodeB 804, respectively. TheUE 802 is connected to the source eNodeB 804 in a communication up tothe step 6. In a communication between the UE receiving a response tothe synchronization and the RACH procedure in the step 6, and theoccurrence of the step 11, dual connectivity for the UE 802 isperformed, wherein the source eNodeB 804 may represent the RRC anchornode. From the step 11 onwards, the UE 802 is connected to the sourceeNodeB 804, but not to the assisting eNodeB 808. Afterwards, the sourceeNB 804 may send a path switch request to a core network node.

Hence, after the UE 802 has measured a Layer-3 RLF (i.e. timer T310expired) towards the assisting cell (FIG. 8), it will stop thetransmission on this link and trigger the transmission of the RLFwarning message, as further described below, towards the source eNB 804.The source eNB 804 will send an indication to the assisting eNB 808 tostop the RRC relaying functionality (8) for the UE 802, since it isaware of the UE 802 having triggered RLF to the assisting eNB 808. Thisway the assisting eNB 808 is informed about the radio link failure tothe UE 802 immediately, which would not have been possible with thecurrently standardized solution, where this state could only beestimated based on timers etc. At this point RRC diversity should bedeactivated in both source eNB 804 and assisting eNB 808. Only theconnection between source eNB 804 and UE 802 should be maintained, thusthe UE 802 is configured to stop RRC diversity, but maintain theconnection to the UE 802. The source eNB 804 uses the RRCreconfiguration procedure (10, 11) to reconfigure the UE 802 to leaveRRC diversity mode and be solely connected to the source cell.

Provided the system is capable of dual connectivity for the UE 802, alsopotential bearers terminated at the assisting eNB 808 would bereconfigured to terminate at the source eNB 804. For this, the sourceeNB 804 also sends a path switch command towards the core network sothat the packets are routed to the source eNB 804.

Accordingly, FIG. 8 illustrates a Radio link failure (RLF) warning forthe assisting eNB 808 out-of-sync.

In the following, a reaction to a source eNB 904 out-of-sync isdescribed. In a step 994, a RLF between the UE 902 and the source eNodeB904 has occurred. In a step 996, the UE 902 stops transmission to thesource eNodeB 904. Thereupon in a step 7, a RLF warning is sent from theUE 902 to the source eNodeB 904 via the assisting eNodeB 908. In a step8, the source eNodeB 904 sends a handover request to the assistingeNodeB 908. In a step 9, the assisting eNodeB 908 sends a handoveracknowledgement to the source eNodeB 904. In a step 11, the sourceeNodeB 904 sends a RRC reconfiguration request via the assisting eNodeB908 to the user equipment UE 902. In a step 998, the source eNodeB 904stops RRC diversity and the assisting eNodeB 908 upgrades to the RRCanchor in a step 999 for the UE 902. In a step 12, the source eNodeB 904sends a sequence number status transfer to the assisting eNodeB 908, andthe UE 902 sends in a step 13 a RRC reconfiguration command to theassisting eNodeB 908. In a step 14, the assisting eNodeB 908 sends a UEcontext release message to the source eNodeB 904. In a communication upto the receipt of the synchronization and RACH procedure related messagereceived by the UE 902, the UE 902 is connected to the source eNodeB904. In a time interval between the UE 902 receiving the message in thestep 6 and the message transfer in the step 13 taking place, dualconnectivity for the UE 902 is performed in which the source eNodeB 904is the RRC anchor node. From the step 13 onwards, the UE 902 isconnected to the assistant eNodeB 908.

Hence, in FIG. 9 RLF on the link to the source eNB 904 occurs and isregistered within the UE 902. It will stop its transmission on this linkand transmit an RLF warning indication towards the assisting eNB 908 (7)which will (since it is in RRC relaying mode) further forward thisindication towards the source eNB 904. The source eNB 904 will thenhandover the UE 902 completely to the assisting eNB 908 since it can besure the connection source 904-UE 902 is lost. Therefore, it will sendthe handover request indication (8) to the assisting eNB 908, which isacknowledged (9) by the assisting eNB 908. The acknowledgment alsoincludes the handover command for the UE 902, which the source eNB 904is supposed to send to the UE 902. The source eNB 904 will send thehandover command (RRC reconfiguration (11)) via the RRC relay, i.e. theassisting eNB 908, to the UE 902. Therefore, it is important that theassisting eNB 908 still remains in RRC relaying mode, even though itreceived and acknowledges the complete handover of the UE 902 already.After relaying the handover command to the UE 902, the assisting eNB 908can upgrade itself to be the RRC anchor for the UE 902. The source eNB904 can stop RRC diversity. Both nodes 904, 908 will now follow thestandardized HO procedure, i.e. source eNB 904 will send sequence numberstatus transfer (12) to the assisting eNB 908 and forward bufferedpackets. The UE 902 will confirm the RRC reconfiguration to be solelyconnected to the assisting (now anchor) eNB 908 (13), and eventually theassisting eNB 908 will send the UE context release indication to thesource eNB 904 (14).

In another embodiment, the assisting eNB 908 being in RRC relaying modefor the UE 902, will transmit the handover command to the UE 902 (11)itself in case the source requests a complete handover. In this variant,the handover request acknowledge message does not need to include thehandover command for the UE 902, since the source eNB 904 is notsupposed to transmit it anyway. However, the source eNB 904 needs to beinformed that the UE 902 is handed over to the assisting eNB 908 andthat SN status transfer and buffered data transfer needs to beinitiated.

In another embodiment, the assisting eNB 908 could also inspect the RLFwarning it forwards and directly send handover acknowledgment to thesource eNB 904, as well as handover command to the UE 902 itself.

Accordingly, FIG. 9 illustrates a radio link failure (RLF) warning forthe source eNB out-of-sync.

In the following, radio link failure related actions according toembodiments are described.

It is assumed that the current RLF procedure is only triggered if theconditions for RLF on all links are fulfilled simultaneously. Therefore,RRC needs to evaluate physical layer problems of all links separately.

The timers and constants for the UE 802, 902 to evaluate physical layerproblems shall be configurable on a per link basis, thus multipleinstances of the IE rlf-TimersAndConstants (or at least a subset of thecorresponding timers/constants, e.g. T310, N310, N311) shall exist andbe configurable in the UE 802, 902. In another embodiment, the samevalues are applied to the each of the links, but evaluation is stilldone independently.

In the following a RLF-TimersAndConstants information element permaintained connection is illustrated. In this information element, theabove mentioned timers and constants may be included.

-- ASN1START RLF-TimersAndConstants-r9 ::= CHOICE { release NULL, setupSEQUENCE { t301-r9 ENUMERATED { ms100, ms200, ms300, ms400, ms600,ms1000, ms1500, ms2000}, t310-r9 ENUMERATED { ms0, ms50, ms100, ms200,ms500, ms1000, ms2000}, n310-r9 ENUMERATED { n1, n2, n3, n4, n6, n8,n10, n20}, t311-r9 ENUMERATED { ms1000, ms3000, ms5000, ms10000,ms15000, ms20000, ms30000}, n311-r9 ENUMERATED { n1, n2, n3, n4, n5, n6,n8, n10}, ... } } -- ASN1STOP

To detect a physical layer problem in RRC_CONNECTED, the UE 802, 902evaluates separately per connected cell i if N310i consecutive“out-of-sync” indications are received from lower layers while neitherin T300 i, T301 i, T304 i, T311 i and then starts timer T310 i. Uponreceiving N311 i consecutive “in-sync” indications from lower layerswhile T310 i is running, the UE shall stop timer T310 i. The separateevaluation on a per link basis shall also apply if further advancedtechniques of “out-of-sync”/“in-sync” evaluations are applied, e.g.additionally evaluating whether a measurement report was sent.

In the following a RLF-warning procedure according to embodiments isdescribed.

Upon T310 expiry of a certain cell, or maximum number of schedulingrequests is reached, or RLC maximum number of retransmissions reachedindication for this cell, the UE 802, 902 shall trigger the newRLF-warning procedure as defined in the following.

The UE 802, 902 shall trigger the following modified actions and preparethe RLF-warning indication to be sent directly via a second maintainedconnection. Additionally the legacy RLF-Report is prepared in a modifiedway.

The following two pseudo code examples may describe the methodembodiments of FIGS. 8, 9 with respect to a RLF procedure according toTS 36.331 V11.2.0 (2012-12), section 5.3.11.3 “Detection of RLF”. Forease of clarity, not changed pseudo code portions may have been omitted.In particular, deviations from this standard can be deduced by means ofcomparison with the pseudo code examples and are presented in bold forease of visibility. The first pseudo code example may relate to a methodembodiment in which the terminal 802, 902 may stop transmitting andreceiving via the degraded or failed connection, hence may stopcommunicating both in an uplink direction and a downlink direction. Thesecond pseudo code example may relate to method embodiment in which theterminal may continue transmitting in an uplink direction via thedegraded or failed connection to the respective access node 804, 808,904, 908 but may not receive any information via the degraded or failedconnection towards the respective access node 804, 808, 904, 908.

Alternative 1:

2> don't consider radio link failure to be detected;

2> store the following radio link failure information in the modifiedVarRLF-Report according to the selection of links to transmit the RLFwarning described below or according to the RLF warning contentsdescribed below

2> if AS security has not been activated:

-   -   3> don't perform the actions upon leaving RRC_CONNECTED as        specified in 36.331/5.3.12, with release cause ‘other’;

2> else:

-   -   3> don't initiate the connection re-establishment procedure as        specified in 36.331/5.3.7;

2> stop transmission and reception on the link for which RLF is detected

2> trigger transmission of the new RLF-warning indication from the UE toE-UTRA via one or multiple of the other maintained connections

Alternative 2:

2> don't consider radio link failure to be detected;

2> store the following radio link failure information in the modifiedVarRLF-Report according to the RLF warning contents described below

2> if AS security has not been activated:

-   -   3> don't perform the actions upon leaving RRC_CONNECTED as        specified in 36.331/5.3.12, with release cause ‘other’;

2> else:

-   -   3> don't initiate the connection re-establishment procedure as        specified in 36.331/5.3.7;

2> trigger transmission of the new RLF-warning indication from the UE toE-UTRA via one or multiple of the other maintained connections

With alternative 2 the terminal 802, 902 does not stoptransmission/reception on the link for which T310 has expired. Expiry ofT310 only means that the downlink channel has problem due to poorchannel quality but this does not mean that there are any problems inuplink. The uplink transmissions may therefore successfully reach thebase station 804, 808, 904, 908. This is expected to be beneficialespecially in case the acknowledgements for the terminals uplinktransmissions can be transmitted from the network to the terminal 802,902 on an alternative link, for example a link for which RLF has notbeen detected.

If the terminal 802, 902 continues to transmit and receive (attempt toreceive) on the link for which T310 has expired then it is possible thatif the link later becomes better after RLF has been detected theterminal 802, 902 can resume use of that link.

For example, the terminal 802, 902 may detect a RLF on a connection toone access node 804, 808, 904, 908 of the source access node 804, 904and the assisting access node 808, 908, the terminal 802, 902 may send,in a first option, the RLF indication to the respective other accessnode 804, 808, 904, 908 which may forward the RLF indication to theaccess node 804, 808, 904, 908 associated with the detected RLF. Theterminal 802, 902 may stop transmission and/or reception to the accessnode 804, 808, 904, 908 associated with the detected RLF or may continuetransmission and/or reception to the access node 804, 808, 904, 908associated with the detected RLF. In a second option, the terminal 802,902 may send the RLF indication to the access node 804, 808, 904, 908associated with the detected RLF. The terminal 802, 902 might not stoptransmission and/or reception to this access node 804, 808, 904, 908 inthis case. The access node 804, 808, 904, 908 may in turn forward theRLF warning to the other access node 804, 808, 904, 908 not beingassociated with the detected RLF.

In the following a selection of links to transmit the RLF-warningaccording to embodiments is described.

The terminal 802, 902 may select a set of configured links on which itsends the RLF-warning on. For example, it may send the RLF-warning toall cells or a subset of all configured links such as only on the sourcelink.

If the terminal 802, 902 knows that it has one or more alternative linksto the node 804, 808, 904, 908 offering the link for which T310 hasexpired, for example if there are two links from a node to a terminal802, 902 and T310 expires only for one of these links then it would bebeneficial to transmit the RLF-warning on one or more alternative links.

The terminal 802, 902 may even send the RLF-warning on the link forwhich the T310 has expired. The benefit of sending the RLF-warning onthe link for which T310 has expired is that the concerned node 804, 808,904, 908 may need to be informed about the expiration of T310. Theexpiration of T310 indicates that the downlink quality is poor howeverthe uplink may still have sufficiently good quality allowing theRLF-warning to reach the concerned node 804, 808, 904, 908.

In the following, RLF-warning contents according to embodiments aredescribed.

(1) This RLF-warning message indicates to E-UTRA that one of themaintained connections is lost. It can optionally include a subset ofthe information from the legacy RLF-Report, as well as details of thefailure reason. It may further include an indicator to which connectionthe RFL-warning belongs. A non-exhaustive list of potential fields forthe RLF-warning is given in the following. Information of the cell theRLF-warning belongs to

-   -   Primary Cell (PCell) Identification (ID), cell global ID,        physical cell ID, carrier frequency of this cell

(2) Latest or historic measurement results for the cell the RLF-warningbelongs to

-   -   Reference Signal Received Power (RSRP), Reference Signal        Received Quality (RSRQ), or other

(3) Latest or historic measurement results for other serving cells

-   -   RSRP, RSRQ, etc., cell identifiers for the respective        measurements

(4) Latest or historic measurement results for non-serving neighborcells

-   -   E-UTRA, UMTS Terrestrial Radio Access (UTRA), Global System for        Mobile Communications (GSM) Enhanced data rates for GSM        evolution (EDGE) Radio Access Network (GERAN), CDMA2000, or        other systems measurements

(5) Time of failure

(6) Detailed failure type and reason

-   -   Out-of-sync, maximum number of scheduling requests, RLF        retransmissions reached, etc.

(7) UE state information, list of current events, e.g. measurementevents.

(8) Buffer status

In the following, modified RLF-reporting according to embodiments isdescribed. This kind of RLF reporting may be regarded to be modifiedwith respect to legacy RLF reporting according to TS 36.331 V11.2.0(2012-12) which may be directed to RFL reporting for a single connectionbetween a terminal 802, 902 and an access node 804, 808, 904, 908.

In the original RLF reporting, the UE 802, 902 stores RLF relatedinformation for the (single) link where the failure occurred and sendsthe report to E-UTRAN upon request. The report is overridden whenanother RLF occurs. In RRC diversity, the UE 802, 902 shall trigger theoriginal RLF procedure as well as the original RLF report only if alllinks fail. So, this reporting can be modified to convey informationabout multiple links.

In one embodiment, the single modified RLF report can includeinformation about multiple or all links.

In another embodiment, multiple RLF reports, so one per link can becreated and requested independently or collectively by E-UTRA.

In the following, Channel Quality Indicator (CQI) monitoring in networkis described. A CQI information or report may represent an alternativeembodiment for the quality degradation information with respect to RFLwarning indications described above.

As an alternative to using RLF-warnings in the network to triggerRRC-reconfigurations for the UE 802, 902 as explained above, CQI reportsreceived for each link in the respective network node 804, 808, 904, 908can be forwarded to another node 804, 808, 904, 908, which is alsocurrently connected to the UE 802, 902. For example, in the case inwhich the source eNodeB 804, 904 may be associated with a connectionquality degradation, the CQI received by the source eNodeB 804, 904 maybe transmitted to the assisting eNodeB 808, 908. In the case in whichthe assisting eNodeB 808, 908 may be associated with a connectionquality degradation, the CQI report received by the assisting eNodeB804, 904 may be sent to the source eNodeB 804, 904. In one embodimentthe network will monitor the received CQI reports received from theterminal 802, 902 regarding the terminal's different connections. If thereported CQI indicates a channel quality for one connection below acertain threshold the network will consider that connection unfit foruse by the terminal 802, 902.

In case the network considers the quality of a connection is not goodenough and unfit for use by the terminal 802, 902 it may take actionssuch as the following. Note that different behavior may be applieddepending on which type of connection is concerned:

(1) Trigger a handover—The network can order the terminal 802, 902 toperform a handover to another, probably better quality, cell. If theconnection with bad quality is the source cell this is one alternativeto ensuring that another cell becomes the source connection. In case theassisting cell has been identified to be of better quality than thesource cell, a similar procedure such as described above for thereaction to a source eNB out-of-syn can be envisaged.

(2) Source and assisting cell switch—If the network detects that thesource cell's quality is below a certain threshold while the quality ofan assisting cell is acceptable the network could trigger a switch sothat an assisting cell instead becomes the source cell and the sourcecell instead becomes an assisting cell. This is similar to a handoverhowever it may not include the RRC-reconfiguration in the UE 802, 902,since the UE 802, 902 can be oblivious of the network element 804, 808,904, 908 acting as the RRC anchor.

(3) Deconfigure the assisting cell—If the quality of a cell which isserving as an assisting cell is bad the motivation to keep the assistingcell. The network may therefore deconfigure the assisting cell. In caseafter the deconfiguration of the assisting cell the terminal 802, 902 isonly configured with the source cell RRC diversity may be de-configured.This behavior is similar to the procedure described above for a reactionto an assisting eNB out-of-sync.

In the following, RLF-warnings for UL/DL trouble shooting in E-UTRANaccording to embodiments are described.

Whenever an RLF warning occurs for one link of the connection (triggerede.g. by out-of-sync, maximum number of scheduling requests reached ormaximum number of RLC retransmission reached) the receiving eNB 804,808, 904, 908 can utilize the information about failure reason and UEmeasurements etc. as given in the warning message by combining it withits own information about the working link, e.g. about current eventsand transmissions done to UE. So, with the RLF warning procedure,E-UTRAN is able to combine UE and eNB information to determine if theproblem was related to that eNB 804, 808, 904, 908 did not receive theUE 802, 902 on the link where problems was indicated or vice versa orboth.

Also the eNB 804, 808, 904, 908 may experience similar faults as the UE802, 902 e.g. maximum number of resynch attempts reached, maximum numberof scheduling requests reached or maximum number of RLC retransmissionreached and then eNB 804, 808, 904, 908 could ask the UE 802, 902 toprovide historic data about UE events and transmissions done. Thisfunctionality can be established with another request/response messageexchange triggered by the eNB 804, 808, 904, 908 and transmitted via oneof the maintained connections.

With the combined information E-UTRAN is able to quickly react uponthese connectivity problems and adapt its system settings to improve theperformance for the UE 802, 902 and the overall system, e.g. certain keyperformance indicators.

Further embodiments are as follows:

In an embodiment, instead of triggering the RLF warning transmissiondepending on the existing T310 timer for this respective link, a newtimer per link is used, which is started simultaneously with the T310timer, but has a different expiry time. This way, RLF warning indicationtransmission can be triggered independently of the existing RLFevaluation per link, thus the RLF warning can be transmitted e.g.earlier than RLF on that link is triggered. Also, second N310 and N311constants per link can be used for this evaluation.

In the following advantages of one or more embodiments are described.

With the provided solution unnecessary transmissions between a UE 802,902 and an eNB 804, 808, 904, 908 are avoided in RRC diversity mode. Inthis way interference and battery consumption are decreased. With thediscussed procedures the UE 802, 902 is able to maintain an RRCconnection when experiencing RLF on one link in a diversity transmissionmode. A fast fallback (or fast fall-forward) to one of the maintainedconnections if one of the connections fails is ensured.

Moreover, this solution will allow an operator to understand the rootcause for intermittent performance degradations in a radio network andespecially understand if it is a network problem or a UE problem orboth. The method will also work in rather poor conditions since only oneout of several connections to the network need to work.

With this solution the system is able to very quickly adapt to UEconnectivity problems and adapt the system to improve the system'sperformance.

Referring to FIG. 10, a terminal 1002 for adapting a mobile network isdescribed. For example, the terminal 1002 may correspond to the terminal802 or 902. The terminal 1002 is connected to a first access node of themobile network via a first connection and to a second access node via asecond connection. The first access node controls a data transmissionfor the terminal 1002 and wherein the second access node assists in thedata transmission for the terminal 1002. The terminal 1002 may compriseone or more interfaces 1003 to the first and second access nodes. Theone or more interfaces 1003 may be coupled each to a processor 1005 ofthe terminal 1002, which processor 1005 has access to a memory 1007 ofthe terminal 1002.

The terminal 1002 comprises a determination unit 1009 adapted todetermining whether a quality of at least one of the first connectionand the second connection is degraded, and an acquiring unit 1011adapted to acquire quality degradation information about the degradationof the quality of at least one of the first connection and the secondconnection based on the determination for adapting the mobile networkbased on the acquired quality degradation information. In a furtherimplementation, the terminal 1002 may comprise a determination unit 1009adapted to determining whether a quality of at least one of the firstconnection and the second connection may be degraded, and an acquiringunit 1011 adapted to acquire quality degradation information about thedegradation of the quality of at least one of the first connection andthe second connection based on the determination particularly foradapting the mobile network.

In the above two described implementations, the determination unit 1009may be part of the processor 1005. Further, the acquiring unit 1011 maybe part of the one or more interfaces 1003. The one or more interfaces1003 may further comprise a reception unit 1013 and a sending unit 1015for implementing receiving and sending capabilities of the one or moreinterfaces 1003, respectively. The sending unit 1015 may implement abovedescribed functionalities related to sending the quality degradationinformation.

The terminal 1002 is adapted to perform a method according toembodiments described above and comprises respective functionality basedunits imbedded in respective physical units 1003, 1005, 1007 illustratedin FIG. 10.

Referring to FIG. 11, an access node 1104 for adapting a mobile networkis illustrated. For example, the access node 1104 may correspond to thefirst access node 804, 904. A terminal is connected to the access node1104 of the mobile network via a connection and to another access nodevia another second connection. The access node 1104 controls a datatransmission for the terminal and the another access node assists in thedata transmission for the terminal. The access node 1004 may compriseone or more interfaces 1103 to the terminal and the another access node.The one or more interfaces 1103 may be coupled each to a processor 1105of the access node 1104, which processor 1005 has access to a memory1107 of the access node 1104.

The access node 1104 comprises an acquiring unit 1111 adapted to acquirequality degradation information about a degradation of a quality of atleast one of the first connection and the second connection based on adetermination whether the quality of at least one of the firstconnection and the second connection is degraded, and an adapting unit1117 adapted to adapt the mobile network based on the acquired qualitydegradation information. In a further implementation, the access node1104 may comprise an acquiring unit 1111 adapted to acquire qualitydegradation information about a degradation of a quality of at least oneof the first connection and the second connection. For example, thequality degradation information may be based on a determination whetherthe quality of at least one of the first connection and the secondconnection may be degraded. In this further implementation, the accessnode 1104 may comprise an adapting unit 1117 adapted to adapt the mobilenetwork based on the acquired quality degradation information. In bothimplementations, the access node 1104 may further comprise adetermination unit adapted to determine whether the quality of at leastone of the connection and the another connection may be degraded.

In the above two implementations, the acquiring unit 1111 and theadapting unit 1117 may be part of the one or more interfaces 1103. Theone or more interfaces 1103 may further comprise a reception unit 1113and a sending unit 1115 for implementing receiving and sendingcapabilities of the one or more interfaces 1103, respectively. Thedetermination unit may be part of the processor 1105.

The access node 1104 is adapted to perform a method according toembodiments described above and comprises respective functionality basedunits imbedded in respective physical units 1103, 1105, 1107 illustratedin FIG. 11.

Referring to FIG. 12, an access node 1208 for adapting a mobile networkis illustrated. For example, the access node 1208 may correspond to theaccess node 808, 908. A terminal is connected to the access node 1208 ofthe mobile network via a connection and to another access node viaanother connection. The another access node controls a data transmissionfor the terminal and the access node 1208 assists in the datatransmission for the terminal. The access node 1208 may comprise one ormore interfaces 1103 to the terminal and the another access node. Theone or more interfaces 1203 may be coupled each to a processor 1205 ofthe access node 1208, which processor 1205 has access to a memory 1107of the access node 1208.

The access node 1208 comprises an adapting unit 1217 adapted to adaptthe mobile network based on acquired quality degradation informationabout a degradation of a quality of at least one of the connection andthe another connection, the acquiring of the quality degradationinformation being based on a determination whether a quality of at leastone of the connection and the another connection is degraded. In afurther implementation, the access node 1208 may comprise an adaptingunit 1217 adapted to adapt the mobile network based on a quality of atleast one of the connection and the another connection being degraded.In this implementation, the adapting unit 1217 unit may be adapted toperform the adaption based on acquired quality degradation informationabout a degradation of a quality of at least one of the connection andthe another connection. The acquiring of the quality degradationinformation may be based on a determination whether a quality of atleast one of the connection and the another connection is degraded.

In both latter implementations, the access node 1208 may comprise anacquiring unit 1211 adapted to acquire the quality degradationinformation. In both latter described implementations, the access node1208 may also comprise a determination unit 1209 adapted to determinewhether the quality of at least one of the connection and the anotherconnection may be degraded.

The adapting unit 1217 may be part of the one or more interfaces 1203,and the acquiring unit 1011 may be also part of the one or moreinterfaces 1203. The one or more interfaces 1203 may further comprise areception unit 1213 and a sending unit 1215 for implementing receivingand sending capabilities of the one or more interfaces 1203,respectively. The determination unit 1209 may be part of the processor1205.

The access node 1208 is adapted to perform a method according toembodiments described above and comprises respective functionality basedunits imbedded in respective physical units 1203, 1205, 1207 illustratedin FIG. 12.

It is noted that the described functionality based units 1009 to 1015,1109 to 1117, 1209 to 1217 for implementing the above describedfunctionalities of the respective entity 1002, 1104, 1208 may be alsorealized in software and/or in hardware and software. To this end,suitable configured computer program code may be stored for implementingthe above-described functionalities of the respective entity 1002, 1104,1208 in the memory 1007, 1107, 1207 of the respective above describedentity 1002, 1104, 1208. The memory 1007, 1107, 1207 and the computerprogram code may form a computer program product. The computer programcode may be also stored on a different memory loadable into the memory1007, 1107, 1207 of the respective entity 1002, 1104, 1208. The computerprogram code may be also provided in a downloadable form, forming afurther computer program product.

It is noted that an association between the physical units 1003 to 1007,1103 to 1107, 1203 to 1207 of the terminal 1002 and access nodes 1104,1208 illustrated in FIGS. 10 to 12, respectively, and the functionalitybased units 1009 to 1015, 1109 to 1117, 1209 to 1217 of the terminal1002 and access nodes 1104, 1204 illustrated these Figures,respectively, may differ from the described embodiments. For example,the acquiring unit 1011 of the terminal 1002 illustrated in FIG. 10 maybe part of the interface 1003, the processor 1005, and the memory 1007of the terminal 1002.

It is noted that the embodiments are applicable to LTE and radio accessnetworks of GSM and UMTS.

In the following, various further embodiments of the present disclosurewill be described.

1. A method embodiment for adapting a mobile network, wherein a terminalis connected to a first access node of the mobile network via a firstconnection and to a second access node via a second connection, whereinthe first access node controls a data transmission for the terminal andwherein the second access node assists in the data transmission for theterminal, the method comprising:

-   -   determining whether a quality of at least one of the first        connection and the second connection is degraded,    -   acquiring quality degradation information about the degradation        of the quality of at least one of the first connection and the        second connection based on the step of determining, and    -   adapting the mobile network based on the step of acquiring.

In particular, the terminal is part of the mobile network.

In particular, the term “the first access node controlling a datatransmission of the terminal” may particularly denote to control, by thefirst access node, of resource allocation for uplink and/or downlinkdata transmission for the terminal and/or a connectivity state of theterminal. In particular, the first access node can be referred to as ananchor node for the data transmission of the terminal, for example,always being employed for the data transmission for the terminal. Forexample, in LTE the controlling of the data transmission may compriseterminating a protocol related to the allocation of resources via theair interface between the terminal and the first access node,particularly a RRC protocol, in the first access node.

In particular, the term “the second access node assisting in the datatransmission for the terminal” may particularly denote that the secondaccess node may be free of a capability of controlling the datatransmission to the terminal by may relay the uplink and/or downlinkdata transmission between the access node and the terminal. Inparticular, the second access node can be referred to as a booster nodefor the data transmission of the terminal, for example, being employedfor the data transmission for the terminal as relay node. Hence,information sent between the first access node and the terminal may beduplicatedly sent between the first access node and the terminal via thesecond access node.

In particular, the term “data transmission” may comprise transmission ofsignaling data and/or payload data in the uplink direction from theterminal to the mobile network and/or downlink direction from the mobilenetwork to the terminal.

In particular, the first connection and the second connection may beindependent from one another and may comprise respective radio bearersto be established related to the data transmission.

In particular, the first access node is referred in describedembodiments as “Source eNB” and the first connection is labeled in FIG.4 by “anchor”. In particular, the second access node is referenced indescribed embodiments as “Assisting eNB”. The second connection islabeled in FIG. 4 by “booster” It is noted that the target eNB describedin connection with FIGS. 1A, 1B, and 2 also represents an access nodeadapted to control the data transmission for the terminal.

In particular, in the data transmission for the terminal, data are sentfrom the first access node to the terminal and data duplicates are sentfrom the second access node to the terminal. The first access node mayhave duplicated the respective data and hay have sent the dataduplicates to the second access node.

2. The method according to embodiment 1, wherein the step of determiningresults in the first connection having failed, wherein the step ofadapting comprises:

-   -   maintaining the connection which is not failed.

3. The method according to any preceding embodiment, wherein the step ofdetermining results in the first connection having failed, wherein thestep of adapting comprises:

-   -   handing, by the first access node, the terminal over from the        first access node to the second access node and disconnecting        the first connection.

For example, the first access node may initiate the handover of theterminal by sending a handover request to the second access node. Thesecond access node may forward or relay the handover request to theterminal. The first access node may stop controlling the datatransmission of the terminal. In LTE the latter may relate to stop RRCdiversity. In RRC diversity employed in the first access node may relateto a sending of data directly to the terminal and to a sending ofduplicates of the data, which are sent by the first access node to theterminal, to the second access node for relaying them by the secondaccess node to the terminal. Accordingly, stopping RRC diversity mayrefer to not duplicating the sent data anymore, thus maintaining onlythe direct connection to the terminal to keep a legacy functionality. Orin other words, particularly with respect to LTE, the latter may relateto stopping RRC signal duplication and forwarding to the second accessnode.

4. The method according to embodiment 3, wherein the step of adaptingfurther comprises:

-   -   transferring, by the first access node, control capabilities for        controlling the data transmission of the terminal from the first        access node to the second access node.

In particular, embodiments 3 and 4 are described with reference to FIG.9.

5. The method according to any preceding embodiment, wherein the step ofdetermining results in the second connection having failed, wherein thestep of adapting comprises:

-   -   requesting, by the first access node, to disconnect the second        connection, and    -   stopping to employ the second access node for the data        transmission for the terminal.

In particular, the step of stopping to employ the second access node forthe data transmission may comprise stopping to duplicate the data sentfrom the first access node to the terminal and stopping to send theduplicated data to the second access node. In particular, this step maybe embodied as stopping RRC diversity, relating to not duplicating thedata or messages anymore which may be to be sent to the second accessnode. Thus only a direct connection from the first access node to the UEmay be maintained, the latter referring to as legacy functionality ofthe first access node of the mobile network.

In particular, embodiment 5 is described with reference to FIG. 8.

6. The method according to any preceding embodiment, wherein the step ofdetermining results in one connection of the first connection and thesecond connection having failed, wherein the step of acquiringcomprises:

-   -   sending, by the terminal, the quality degradation information to        the access node of the first access node and the second access        node whose connection to the terminal has not failed.

In particular, the quality degradation information may be sent to thefirst access node, if the second connection may have failed, asexplained with reference to FIG. 8. The quality degradation informationmay be sent to the second access node, if the first connection may havefailed, and may be relayed or forwarded by the second access node to thefirst access node.

7. The method according the embodiment 6, wherein the qualitydegradation information comprises a failure notification indication,particularly a RLF warning indication as explained above.

In particular, the failure notification indication may represent anindividual indication, particularly included in a conventional messageor a new type message, or may be a specific type of message.

In particular, in accordance with any preceding embodiment, the qualitydegradation information may comprise at least one information selectedfrom the group of:

-   -   a cell identification indication indicative of an identification        of an area, particularly a cell, being served by the access node        associated with the failed connection, particularly an PCell        Identification (ID), a cell global ID, a physical cell ID, a        carrier frequency of the cell,    -   information about measurement results obtained for the area        served by the access node associated with the failed connection        and obtained for a previous time period,    -   information about measurement result obtained for an area,        particularly a cell, served by the access node associated with        the not failed connection and obtained for a previous time        period,    -   information about a measurement result obtained for at least one        further area, particularly a further cell, served by a further        access node distinct from the first access node and second        access node and obtained for a previous time period,        particularly an identifier for the measurement    -   a connection indication indicative of the failed connection,    -   a timer of the failure of the failed connection, and    -   a failure reason.

In particular, the failure reason may comprise at least one of thefollowing:

-   -   an expiration of a timer, the timer being started after a        predetermined number of a counter fulfillments of a condition        and the timer being stopped after a predetermined number of        counter fulfillments of another condition; for example in LTE        the latter may correspond to “Out of sync” referring to a RLF        timer expiry,    -   a maximum of scheduling requests having been sent over the        respective connection; for example in LTE the latter may        correspond to a maximum number of RLC retransmissions having        been reached,    -   a maximum of retransmission of data having been sent by the        terminal over the respective connection; for example in LTE the        latter may correspond a maximum number of scheduling requests        having been reached; and    -   a maximum of unsuccessful random access attempts having been        sent by the terminal over the respective connection without        receiving a data transmission over the respective connection;        for example in LTE the latter may correspond to a Random Access        Channel (RACH) failure.

In particular, the at least one information mentioned above may be senttogether with the failure notification indication in one message or maybe sent subsequent to the sent failure notification indication for thestep of acquiring.

8. The method according to any preceding embodiment, wherein the step ofdetermining results in the first connection and the second connectionhaving failed, wherein the step of adapting comprises

-   -   establishing a further connection between the terminal and a        further access node of the mobile network.

In particular, in accordance with the preceding embodiment, the step ofacquiring may be performed by the terminal. The step of establishing maybe initiated by the terminal. The further access node may be distinctfrom the first access node and the second access node or may be one ofthe first and second access nodes.

9. The method according to any preceding embodiment, the method furthercomprising:

-   -   determining at least one key performance indication for the        mobile network, wherein the step of adapting comprises adapting        at least one system setting of the mobile network based on the        at least one key performance indication.

In particular, the step of adapting of the system settings may bealternatively or additionally based on quality degradation informationobtained, particularly sent in RLF reports. An objective of thisadaption may be the improvement of one of the key performance indicatorsin the network.

In particular, the system setting may relate to a characteristic of thefirst and/or second access node or may relate to a characteristic of afurther access node of the mobile network.

In particular, embodiments 2 to 8 may describe an immediate or ad hocadapted of the mobile network. Embodiments 9 may describe an overalladaption of the mobile network on an intermediate or long term timescale.

10. The method according to any preceding embodiment, wherein the stepof determining is performed by the terminal and comprises evaluating thequality of the first connection and evaluating the quality of the secondconnection.

In particular, the step of evaluating of the quality of the firstconnection and the step of evaluating the quality of the secondconnection is performed independently of one another.

11. The method according to the preceding embodiment, wherein therespective step of evaluating comprises evaluating a synchronization ofthe terminal with the respective access node with respect to the datatransmission over the respective connection.

In particular, a degradation of the quality of the respective connectionmay be determined, if the terminal may be not suitably synchronized forthe data transmission over the respective connection. In particular, thedetermined degradation of the quality of the connection may correspondto a connection failure.

12. The method according to the preceding embodiment, wherein the stepof determining comprises, particularly for each of the first and secondconnections, using a timer in the terminal and a counter in theterminal, the counter being associated with fulfillment of a condition,wherein a degradation of the quality of the respective connection isdetermined, if the timer expires, the timer being started after apredetermined number of the counter fulfillments of the condition, andthe timer being stopped after a predetermined number of counterfulfillments of another condition.

In particular, the timer may correspond to the T310 timer and thecounter may correspond to the constant N310 both described above. Inparticular, the same or different type of timers and/or counters can beemployed for the first and second connections.

In particular, in accordance with any preceding embodiment, the step ofdetermining comprises, particularly for each of the first and secondconnections, using a timer in the terminal and counters in the terminal,one counter being associated with fulfillment of a condition, wherein adegradation of the quality of the respective connection is determined,if the timer expires, the timer being started after a predeterminednumber of the counter fulfillments of the condition, and the timer beingstopped after a predetermined number of another counter fulfillments ofanother condition.

In particular, the timer may correspond to the T310 timer and thecounters may correspond to the constants N310, N311 as described above.In particular, the same or different type of timers and/or counters canbe employed for the first and second connections.

13. The method according to the embodiments 10 to 12, wherein therespective step of evaluating comprises evaluating whether a maximum ofscheduling requests has been sent over the respective connection.

14. The method according to the embodiments 10 to 13, wherein therespective step of evaluating comprises evaluating whether a maximum ofretransmission of data has been sent by the terminal over the respectiveconnection.

15. The method according to the embodiments 10 to 14, wherein therespective step of evaluating comprises evaluating whether a maximum ofunsuccessful random access attempts has been sent by the terminal overthe respective connection without receiving a data transmission over therespective connection.

16. The method according to any preceding embodiment, wherein the stepof acquiring comprises sending by the second access node to the firstaccess the quality degradation information.

In particular, the latter embodiment may apply in a case in which atleast one of the first and second connections may comprise a degraded orlow quality but might not have failed. For example, the qualitydegradation information may comprise a channel quality indication. Thestep of determining may be performed by the second access node which maymonitor a parameter associated with the channel quality informationand/or may determine a value of the parameter.

In particular, the latter embodiment may apply to the embodiment relatedto handing over the terminal and to the embodiment related to thehandover combined with the transfer of the control capabilities.

17. A method embodiment for adapting a mobile network, wherein aterminal is connected to a first access node of the mobile network via afirst connection and to a second access node via a second connection,wherein the first access node controls a data transmission for theterminal and wherein the second access node assists in the datatransmission for the terminal, the method being performed by theterminal and comprising:

-   -   determining whether a quality of at least one of the first        connection and the second connection is degraded,    -   acquiring quality degradation information about the degradation        of the quality of at least one of the first connection and the        second connection based on the step of determining for adapting        the mobile network based on the step of acquiring.

18. A method embodiment for adapting a mobile network, wherein aterminal is connected to a first access node of the mobile network via afirst connection and to a second access node via a second connection,wherein the first access node controls a data transmission for theterminal and wherein the second access node assists in the datatransmission for the terminal, the method being performed by the firstaccess node and comprising:

-   -   acquiring quality degradation information about a degradation of        a quality of at least one of the first connection and the second        connection based on a determination whether the quality of at        least one of the first connection and the second connection is        degraded, and    -   adapting the mobile network based on the step of acquiring.

19. A method embodiment for adapting a mobile network, wherein aterminal is connected to a first access node of the mobile network via afirst connection and to a second access node via a second connection,wherein the first access node controls a data transmission for theterminal and wherein the second access node assists in the datatransmission for the terminal, the method being performed by the secondaccess node and comprising:

-   -   adapting the mobile network based on acquired quality        degradation information about a degradation of a quality of at        least one of the first connection and the second connection, the        acquiring being based on a determination whether a quality of at        least one of the first connection and the second connection is        degraded.

20. A terminal embodiment for adapting a mobile network, wherein theterminal is connected to a first access node of the mobile network via afirst connection and to a second access node via a second connection,wherein the first access node controls a data transmission for theterminal and wherein the second access node assists in the datatransmission for the terminal, the terminal comprising:

-   -   a determination unit adapted to determining whether a quality of        at least one of the first connection and the second connection        is degraded,    -   an acquiring unit adapted to acquire quality degradation        information about the degradation of the quality of at least one        of the first connection and the second connection based on the        determination for adapting the mobile network based on the        acquired quality degradation information.

In particular, the terminal may be adapted to perform a method accordingto any one of embodiments 1 to 18.

21. An access node embodiment for adapting a mobile network, wherein aterminal is connected to the access node of the mobile network via aconnection and to another access node via another second connection,wherein the access node controls a data transmission for the terminaland wherein the another access node assists in the data transmission forthe terminal, the access node comprising:

-   -   an acquiring unit adapted to acquire quality degradation        information about a degradation of a quality of at least one of        the first connection and the second connection based on a        determination whether the quality of at least one of the first        connection and the second connection is degraded, and    -   an adapting unit adapted to adapt the mobile network based on        the acquired quality degradation information.

In particular, the access node may be adapted to perform a methodaccording to any one of embodiments 1 to 17 and 19.

22. An access node embodiment for adapting a mobile network, wherein aterminal is connected to the access node of the mobile network via aconnection and to another access node via another connection, whereinthe another access node controls a data transmission for the terminaland wherein the access node assists in the data transmission for theterminal, the access node comprising:

-   -   an adapting unit adapted to adapt the mobile network based on        acquired quality degradation information about a degradation of        a quality of at least one of the connection and the another        connection, the acquiring of the quality degradation unit being        based on a determination whether a quality of at least one of        the connection and the another connection is degraded.

In particular, the access node may be adapted to perform a methodaccording to anyone of embodiments 1 to 17 and 19.

23. A mobile network embodiment, comprising a terminal according toembodiment 20, a first access node according to embodiment 21, and asecond access node according to embodiment 22.

24. A computer program, which, when being executed by a processor, isadapted to carry out or control a method for handling a terminatingcircuit switched signaling service to a terminal in a mobile networkaccording to any one of embodiments 1 to 19.

It is noted that the above described embodiments related to methodaccording to embodiments 1 to 16 apply to the embodiments related toother methods according to embodiments 17 to 19, the terminal, the firstaccess node, the second access node, a mobile network and the computerprograms.

What is claimed is:
 1. A method for adapting a mobile network, wherein aterminal is connected to a first access node of the mobile network via afirst connection and to a second access node of the mobile network via asecond connection, wherein the first access node controls a datatransmission for the terminal and wherein the second access node assistsin the data transmission for the terminal, the method being performed bythe first access node and comprising: acquiring quality degradationinformation about a degradation of a quality of at least one of thefirst connection and the second connection; and adapting the mobilenetwork based on the step of acquiring.
 2. The method according to claim1, wherein the terminal is simultaneously connected to the first accessnode via the first connection and connected to the second access nodevia the second connection, wherein the first access node controls a datatransmission for the terminal and provides a single control planeconnection for the terminal to a core network of the mobile network, andwherein the second access node assists in the data transmission for theterminal and does not provide a control plane connection for theterminal to the core network.
 3. The method according to claim 1,wherein the step of acquiring comprises receiving the qualitydegradation information from the terminal.
 4. The method according toclaim 1, wherein the quality degradation information comprises a failurenotification indication indicative of a failure of at least one of thefirst connection and the second connection.
 5. The method according toclaim 4, wherein the quality degradation information comprises at leastone information selected from the group of: a cell identificationindication indicative of an identification of a cell served by an accessnode associated with one of the first and the second connections thathas failed; information about measurement results obtained for the cellserved by the access node associated with one of the first and thesecond connections that has failed and obtained for a previous timeperiod; information about a measurement result obtained for a cellserved by an access node associated one of the first and the secondconnections that has not failed and obtained for a previous time period;information about a measurement result obtained for at least one furthercell served by a further access node distinct from the first access nodeand second access node and obtained for a previous time period; and aconnection indication indicative of one of the first and the secondconnections that has failed; a timer of the failure of one of the firstand the second connections that has failed; and a failure reason.
 6. Themethod according to claim 1, wherein the step of adapting the mobilenetwork comprises adapting at least one connection between the terminaland the mobile network based on the step of acquiring.
 7. The methodaccording to claim 1, wherein the step of adapting the mobile networkcomprises: handing the terminal over from the first access node to thesecond access node and disconnecting the first connection; transferringcontrol capabilities for controlling the data transmission of theterminal from the first access node to the second access node;requesting to disconnect the second connection and stopping to employthe second access node for the data transmission for the terminal; orestablishing a further connection between the terminal and a furtheraccess node of the mobile network.
 8. A first access node for adapting amobile network, wherein a terminal is connected to the first access nodeof the mobile network via a first connection and to a second access nodeof the mobile network via a second connection, wherein the first accessnode controls a data transmission for the terminal and wherein thesecond access node assists in the data transmission for the terminal,the first access node comprising: one or more interface circuitsconfigured to connect the access node to the terminal via the firstconnection; and a processing circuit configured to: acquire qualitydegradation information about a degradation of a quality of at least oneof the first connection and the second connection; and adapt the mobilenetwork based on the quality degradation information.
 9. The firstaccess node according to claim 8, wherein the terminal is simultaneouslyconnected to the first access node via the first connection andconnected to the second access node via the second connection, whereinthe first access node controls a data transmission for the terminal andprovides a single control plane connection for the terminal to a corenetwork of the mobile network, and wherein the second access nodeassists in the data transmission for the terminal and does not provide acontrol plane connection for the terminal to the core network.
 10. Thefirst access node according to claim 8, wherein the processing circuitis configured to receive the quality degradation information from theterminal.
 11. The first access node according to claim 8, wherein thequality degradation information comprises a failure notificationindication indicative of a failure of at least one of the firstconnection and the second connection.
 12. The first access nodeaccording to claim 11, wherein the quality degradation informationcomprises at least one information selected from the group of: a cellidentification indication indicative of an identification of a cellserved by an access node associated with one of the first and the secondconnections that has failed; information about measurement resultsobtained for the cell served by the access node associated with one ofthe first and the second connections that has failed and obtained for aprevious time period; information about a measurement result obtainedfor a cell served by an access node associated one of the first and thesecond connections that has not failed and obtained for a previous timeperiod; information about a measurement result obtained for at least onefurther cell served by a further access node distinct from the firstaccess node and second access node and obtained for a previous timeperiod; and a connection indication indicative of one of the first andthe second connections that has failed; a timer of the failure of one ofthe first and the second connections that has failed; and a failurereason.
 13. The first access node according to claim 8, wherein theprocessing circuit is configured to adapt at least one connectionbetween the terminal and the mobile network based on the qualitydegradation information.
 14. The first access node according to claim 8,wherein the processing circuit is configured to adapt the mobile networkby: handing the terminal over from the first access node to the secondaccess node and disconnecting the first connection; transferring controlcapabilities for controlling the data transmission of the terminal fromthe first access node to the second access node; requesting todisconnect the second connection and stopping to employ the secondaccess node for the data transmission for the terminal; or establishinga further connection between the terminal and a further access node ofthe mobile network.
 15. A method performed by a terminal is connected toa first access node of a mobile network via a first connection and to asecond access node via a second connection, wherein the first accessnode controls a data transmission for the terminal and wherein thesecond access node assists in the data transmission for the terminal,the method comprising: acquiring quality degradation information aboutdegradation of a quality of at least one of the first connection and thesecond connection; and sending the quality degradation information tothe first access node.
 16. The method according to claim 15, wherein theterminal is simultaneously connected to the first access node via thefirst connection and connected to the second access node via the secondconnection, wherein the first access node controls a data transmissionfor the terminal and provides a single control plane connection for theterminal to a core network of the mobile network, and wherein the secondaccess node assists in the data transmission for the terminal and doesnot provide a control plane connection for the terminal to the corenetwork.
 17. The method according to claim 15, wherein the qualitydegradation information comprises a failure notification indicationindicative of a failure of at least one of the first connection and thesecond connection.
 18. The method according to claim 17, wherein thequality degradation information comprises at least one informationselected from the group of: a cell identification indication indicativeof an identification of a cell served by an access node associated withone of the first and the second connections that has failed; informationabout measurement results obtained for the cell served by the accessnode associated with one of the first and the second connections thathas failed and obtained for a previous time period; information about ameasurement result obtained for a cell served by an access nodeassociated one of the first and the second connections that has notfailed and obtained for a previous time period; information about ameasurement result obtained for at least one further cell served by afurther access node distinct from the first access node and secondaccess node and obtained for a previous time period; and a connectionindication indicative of one of the first and the second connectionsthat has failed; a timer of the failure of one of the first and thesecond connections that has failed; and a failure reason.
 19. A terminalcomprising: one or more interface circuits; and a processing circuitconfigured to: connect to a first access node of a mobile network via afirst connection and to a second access node via a second connection,wherein the first access node controls a data transmission for theterminal and wherein the second access node assists in the datatransmission for the terminal; acquire quality degradation informationabout degradation of a quality of at least one of the first connectionand the second connection; and send the quality degradation informationto the first access node.
 20. The terminal according to claim 19,wherein the processing circuit is configured to simultaneously connectto the first access node via the first connection and connect to thesecond access node via the second connection, wherein the first accessnode controls a data transmission for the terminal and provides a singlecontrol plane connection for the terminal to a core network of themobile network, and wherein the second access node assists in the datatransmission for the terminal and does not provide a control planeconnection for the terminal to the core network.